One of the most debilitating aspects of Parkinson?s disease is the inability to initiate and execute movements as intended. The fundamental hypothesis behind the proposed research is that basal ganglia impairments, as reflected in Parkinson?s disease, causes a disruption in motor programming processes. It is postulated that there is increased noise in the basal ganglia that produce abnormal timing, patterning, and synchronization of discharges into the motor cortical areas. These irregularities in turn reduce motor programming capabilities that are reflected as alterations in the microstructure of a goal-oriented movement. We have documented that Parkinson?s patients produce movements that exhibit shortened primary submovement components, which then requires secondary, corrective movements. Seven experiments are proposed which examine whether the altered substructure of movements observed in PD is related to muscle activation patterns, force-force variability relationships, and/or a reduced capability to incorporate proprioceptive information at different stages of movement planning and execution. The results of these experiments will be evaluated in combination to allow us to determine which of these potential causes has the greatest impact on primary submovement distance. The data obtained will be useful in the basic science realm as well as the clinical setting; the former by isolating the various motor deficits associated with PD, which may allow for inferences to be made regarding structure-function relationships. In terms of clinical relevance these results will assist in identifying where practitioner interventions or outcome measures should be targeted.